Separation of nine iridoids by capillary electrophoresis and high performance liquid chromatography

A capillary zone electrophoretic (CZE) method and a high-performance liquid chromatographic (HPLC) method were developed for the separation of the nine iridoids, gardenoside, geniposide, geniposidic acid, shanzhiside, loganin, loganic acid, aucubin, harpagoside and catapol. Detection at 210 and 230 nm with a 2,6-di-O-methyl-β-cyclodextrin and sodium borate buffer as carrier or with a linear gradient elution system using acetonitrile and potassium dihydrogenphosphate solution as eluent was found to be the most suitable approach for this separation. The CZE analysis time (32 min) was shorter than that of HPLC (45 min), but the CE method can separate only eight of the nine compounds. The pH, buffer concentration and organic composition of the mobile phase were studied for their effects on the separability of the compounds.